AdBlue® (also called EEF, Diesel Exhaust Fluid), a urea-based liquid, is used for the exhaust gas treatment to reduce nitrogen oxides in automobile diesel engines. Since incorrect filling may occur due to an additional filler neck being provided next to the filler neck for the tank, devices for preventing the incorrect filling of the container for AdBlue® are known.
For example, a device for preventing the incorrect filling of a container of, for example, motor vehicles by means of a delivery nozzle is known from WO 2013/092109 A1, in which the device is provided with a permanent magnet assembly, which has a first permanent magnet subassembly, preferably in the form of an individual magnet in the outlet pipe of the delivery nozzle, wherein the permanent magnet assembly has an additional, second permanent magnet subassembly, which comprises either a plurality of permanent magnets arranged in an annular pattern or an individual magnet, which is arranged in the outlet pipe on the outer circumference of the outlet pipe in a radial alignment with the individual magnet of one subassembly, which said individual magnet acts as a switching magnet.
An assembly unit with a tightly seated ring magnet (NdFeB; remanence: 1.2T-1.3T; coercive field strength 800 kA/m-900 kA/m), which magnet is used to activate a switching magnet of an AdBlue® nozzle when the filler neck is inserted, is correspondingly used in a filler neck known through use.
A device for preventing the incorrect filling of a container, which has permanent magnets, which are arranged in the outlet pipe of the delivery nozzle and are not movable or are only minimally movable in their mount and which interact during the insertion of the delivery nozzle, is known from EP 2 687 479 A1.
DE 10 2004 007 025 A1 discloses a rotatable permanent magnet for indication purposes (type of fuel). The system comprises a magnet ring, which is arranged on the pump nozzle, as well as a magnetic relay and an analysis unit, which is coupled with the magnetic relay and with an optical or acoustic signal transmitter, which are arranged on the tank cap. The magnetic relays, which can close or open a circuit depending on the magnetic field of the pump nozzle, are able to distinguish diesel fuel pumps from gasoline fuel pumps in this manner. One variant can also distinguish different grades of fuel of one type, e.g., regular gasoline from premium grade gasoline. It has a plurality of magnetic relays, which are arranged at different points. When the pump nozzle is approaching the tank cap opening, the magnets in the relays become aligned and correspondingly close the circuits. It is only when the correct magnetic field code is recognized that no alarm is triggered or the closing mechanism is not activated. The magnetic sensor may be arranged here movably or rotatably in a capsule, and it becomes aligned according to the polarity of the magnet of the pump nozzle and recognizes the type of fuel.
Such devices still leave something to be desired, especially in terms of costs.